How many miles are on the car, and what has been replaces so far.

around 80-100k you should have done regular maintance to include stuff like new plugs, wires, dist cap, timing belt and water pump, and a visual inspection of stuff like CV boots and joints and stuff like that

When was the last time you put a bottle of fuel injector cleaner in your fuel tank? You should do it every time you change your oil, every 3000 miles. This will prevent them from getting all clogged and dirty.

if you havn't done any of these maintanance items, then it could be anything you mentioned, or others.

I'm going to copy this to the engine tech forum, so look for it there.